A memorial on Monday outside the Tree of Life Synagogue in Pittsburgh, where 11 people were fatally shot on Saturday. Several groups, including two Muslim organizations, have helped raise money for the victims.CreditCreditMichael Henninger for The New York Times

Two Muslim organizations have raised nearly $200,000 to help victims and their families following the shooting massacre at the Tree of Life Synagogue in Pittsburgh on Saturday.

The online fund-raiser was part of a broad outpouring of assistance in response to the anti-Semitic attack, which killed 11 people and left six others injured, including blood drives, vigils and a separate crowdfunding campaign that has raised hundreds of thousands of dollars.

Tarek El-Messidi, a Chicago-based activist, said he learned of the synagogue shooting in a call Saturday morning from a friend who runs the Muslim fund-raising website LaunchGood. His friend asked Mr. El-Messidi if he could do something to help the victims, and he agreed.

Mr. El-Messidi said he was able to jump-start the campaign and bring in donations so quickly because he has unfortunately done this before. He created a LaunchGood fund-raiser last year that collected $136,000 to repair hundreds of Jewish headstones vandalized in St. Louis and Philadelphia.

“Putting our religious differences or even your political differences aside, the core of all of us is that we have a shared humanity,” Mr. El-Messidi said in an interview. “We really wanted to reach out as human beings to help.”

In the hours after a gunman opened fire inside the Tree of Life synagogue, telling the police that he “wanted all Jews to die,” there was an outpouring of support, within Pittsburgh and beyond, for the victims and their families.

It has served as a reminder of what Fred Rogers, the famed children’s television host who lived within walking distance of the synagogue, said about tragedies: “Always look for the helpers. There are always people who are helping.”

At an interfaith vigil on Sunday evening, Rich Fitzgerald, the top county official in Pittsburgh, spoke about how he had watched people snap into action after the shooting, organize assistance efforts and offer whatever help they could.

“We saw a coming together of people all over this community and all over this region,” Mr. Fitzgerald said at the vigil, held at Soldiers and Sailors Memorial Hall. “Bigotry will not win. Hatred will not win.”

One person who jumped at the chance to help was Shay Khatiri, an Iranian-American who immigrated to the United States four years ago. Mr. Khatiri, who lives in Washington, created a GoFundMe campaign for the synagogue on Saturday.

Over the weekend, donors contributed more than $100,000. Then $200,000. And by Tuesday evening, the campaign had raised nearly $900,000. The latest goal is to bring in $1 million.

Among the donors, “there are Steins and Bergs, and there are Mohammeds. There are generic American names, and there are Asian ones,” Mr. Khatiri wrote on GoFundMe. “It is only fitting that Americans of all backgrounds — immigrant, native-born, Jewish, atheist, Buddhist, Hindu, Christian, Muslim, etc. — are uniting against this hateful act. America is beautiful!”

Mr. El-Messidi said his fund-raiser started to distribute some of the donations on Monday morning. He hopes to raise enough to cover the funeral costs of those who were killed and medical bills for those who were hospitalized.

He said his mind has returned again and again to the story of Prophet Muhammad, the founder of Islam, when he saw a funeral procession for a Jewish man. The prophet stood up to pay his respects. When his disciples next to him noted that the man was not a Muslim, Muhammad replied, “Was he not a soul?”

Mr. El-Messidi said that while Judaism and Islam have their differences, they were linked by a tragic similarity: Followers of both faiths have been targeted in bigoted attacks. “The shared discrimination has brought both communities closer,” he said.